Concern has been expressed that the inquiry committee will be restrained from fully probing the events leading up to the bank guarantee due to the protections afforded to senior ministers.

The committee was told at its first meeting this week that the confidentiality clause could also be applied to meetings involving ministers, bankers and government officials held before the guarantee in September 2008.

This could create a scenario whereby notes and other material relating to the bank guarantee are not probed during the inquiry hearings because of confidentiality.

Article 28 of the Constitution guarantees the confidentiality of cabinet discussions, while two sections of the act governing the bank inquiry restrict the committee from compelling evidence about discussions at cabinet. Privately, a number of members of the committee say they fear former ministers will cite the measures when asked about specific cabinet meetings.

The committee has sought legal advice on the issue from a senior counsel following a request by Fianna Fail's finance spokesman Michael McGrath.

But last night, former minister Eamon Ryan (inset) insisted that ministers must not be able to hide behind cabinet confidentiality when they appear in front of the inquiry.

"There will have to be some leeway in relation to cabinet confidentiality. The more open and transparent the process is, the more freedom members will have to ask questions," he told the Irish Independent.

"It can't be applied so restrictively that witnesses can't say anything," he added.

Mr McGrath said cabinet confidentiality was a "potentially very serious issue".

"We need to have absolute clarity on the issue of cabinet confidentiality in the context of the cabinet deliberations and the eventual decision to introduce the bank guarantee at end of September 2008," he told the Irish Independent. "There needs to be a reassurance that the cabinet discussions, the documentations available to cabinet members, the options looked at, and all supporting documentation can be provided to the committee without anybody breaching constitutional rights."

Oireachtas officials are expected to provide a report on cabinet confidentiality next week.